The present invention relates to an arrangement providing at least two signal generating devices to generate characteristic voltage output signals of different frequency from each generator and of selected voltage where the combined signal of the generators is supplied to an audible sound generating device, for example, an electromagnetic horn.
Devices in accordance with the present invention have a wide range of application, but have been found to be particularly useful as source generating means for an extremely realistic sound emulating the sound of a railroad diesel horn.
Heretofore, model train horns have been driven by single frequency power supplies. While prior art devices have been developed where attempts have been made to simulate the sounds of the air horns utilized currently by most diesel-driven railroad engines, such attempts have generally not been successful.
Additionally, the most successful attempts have resulted in devices which are expensive and therefore unattractive to all but the most avid model railroad follower.
The most commonly available model railroad horn operates in response to a power supply which generates a signal at a generally uniform frequency close to the average frequency of the air horns utilized in connection with diesel railroad engines. Moreover, such devices have been bulky and offensive when utilized in many model railroad layouts which must, in some instances, by mounted beneath the layout, or otherwise disguised, where the sound emanating from the device is muffled.
In general, since the demise of the steam railroad engine and its replacement by the diesel railroad engine, most diesel railroad engines are provided with three horns each operating at a different characteristic frequency so that the apparent instantaneous overall output intensity and frequency is the sum of the instantaneous output of the three horns and the time variation in frequency and intensity of the overall output is likewise dependent on the frequency of the three horns.
In many cases, individual railroads select a combination of horns operating at selected characteristic frequencies so that in some instances the overall apparent sound of a horn package is characteristic of a particular railroad. However, the variation from package to package is not great and at the present time, the overall sound of the horn package utilized by all railroads for their diesel-powered engines is substantially the same.
In current practice, railroad diesel engine horns are airpowered, and, usually, three horns (each operating at a different frequency) are provided to, in the aggregate, provide an output sound where the frequency pattern is non-repetitive or, if repetitive, repeated only infrequently. For example, in one application, the frequency of the three horns is 311 cycles per second, 370 cycles per second, and 470 cycles per second.
In most previous devices providing an electronically driven horn the horn operates at a single frequency at a regularly recurring frequency pattern and is used in an attempt to emulate the sound generated by most railroad engine diesel horns.
Insofar as known, there is no available device to provide an infinitely frequency variable signal generating arrangement to provide the characteristic sound of railroad engine diesel horn. Moreover, there is, insofar as known, no straightforward, inexpensive arrangement available to provide a signal to drive an electromagnetic horn device to reproduce the sound of a diesel horn from a low-voltage power supply where the device is suitable for use in connection with model railroads.